// Copyright (C) 2009-2013, International Business Machines
// Corporation and others. All Rights Reserved.
//
// Copyright 2001 and onwards Google Inc.
// Author: Sanjay Ghemawat

// This code is a contribution of Google code, and the style used here is
// a compromise between the original Google code and the ICU coding guidelines.
// For example, data types are ICU-ified (size_t,int->int32_t),
// and API comments doxygen-ified, but function names and behavior are
// as in the original, if possible.
// Assertion-style error handling, not available in ICU, was changed to
// parameter "pinning" similar to UnicodeString.
//
// In addition, this is only a partial port of the original Google code,
// limited to what was needed so far. The (nearly) complete original code
// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
// (see ICU ticket 6765, r25517).

#ifndef __STRINGPIECE_H__
#define __STRINGPIECE_H__

/**
 * \file 
 * \brief C++ API: StringPiece: Read-only byte string wrapper class.
 */

#include "utypes.h"
#include "uobject.h"
#include "std_string.h"

// Arghh!  I wish C++ literals were "string".

U_NAMESPACE_BEGIN

/**
 * A string-like object that points to a sized piece of memory.
 *
 * We provide non-explicit singleton constructors so users can pass
 * in a "const char*" or a "string" wherever a "StringPiece" is
 * expected.
 *
 * Functions or methods may use const StringPiece& parameters to accept either
 * a "const char*" or a "string" value that will be implicitly converted to
 * a StringPiece.
 *
 * Systematic usage of StringPiece is encouraged as it will reduce unnecessary
 * conversions from "const char*" to "string" and back again.
 *
 * @stable ICU 4.2
 */
class U_COMMON_API StringPiece : public UMemory {
private:
    const char *ptr_;
    int32_t length_;

public:
    /**
     * Default constructor, creates an empty StringPiece.
     * @stable ICU 4.2
     */
    StringPiece() : ptr_(NULL), length_(0) {}

    /**
     * Constructs from a NUL-terminated const char * pointer.
     * @param str a NUL-terminated const char * pointer
     * @stable ICU 4.2
     */
    StringPiece(const char *str);

#if U_HAVE_STD_STRING

    /**
     * Constructs from a std::string.
     * @stable ICU 4.2
     */
    StringPiece(const std::string &str)
            : ptr_(str.data()), length_(static_cast<int32_t>(str.size())) {}

#endif

    /**
     * Constructs from a const char * pointer and a specified length.
     * @param offset a const char * pointer (need not be terminated)
     * @param len the length of the string; must be non-negative
     * @stable ICU 4.2
     */
    StringPiece(const char *offset, int32_t len) : ptr_(offset), length_(len) {}

    /**
     * Substring of another StringPiece.
     * @param x the other StringPiece
     * @param pos start position in x; must be non-negative and <= x.length().
     * @stable ICU 4.2
     */
    StringPiece(const StringPiece &x, int32_t pos);

    /**
     * Substring of another StringPiece.
     * @param x the other StringPiece
     * @param pos start position in x; must be non-negative and <= x.length().
     * @param len length of the substring;
     *            must be non-negative and will be pinned to at most x.length() - pos.
     * @stable ICU 4.2
     */
    StringPiece(const StringPiece &x, int32_t pos, int32_t len);

    /**
     * Returns the string pointer. May be NULL if it is empty.
     *
     * data() may return a pointer to a buffer with embedded NULs, and the
     * returned buffer may or may not be null terminated.  Therefore it is
     * typically a mistake to pass data() to a routine that expects a NUL
     * terminated string.
     * @return the string pointer
     * @stable ICU 4.2
     */
    const char *data() const { return ptr_; }

    /**
     * Returns the string length. Same as length().
     * @return the string length
     * @stable ICU 4.2
     */
    int32_t size() const { return length_; }

    /**
     * Returns the string length. Same as size().
     * @return the string length
     * @stable ICU 4.2
     */
    int32_t length() const { return length_; }

    /**
     * Returns whether the string is empty.
     * @return TRUE if the string is empty
     * @stable ICU 4.2
     */
    UBool empty() const { return length_ == 0; }

    /**
     * Sets to an empty string.
     * @stable ICU 4.2
     */
    void clear() {
        ptr_ = NULL;
        length_ = 0;
    }

    /**
     * Reset the stringpiece to refer to new data.
     * @param xdata pointer the new string data.  Need not be nul terminated.
     * @param len the length of the new data
     * @stable ICU 4.8
     */
    void set(const char *xdata, int32_t len) {
        ptr_ = xdata;
        length_ = len;
    }

    /**
     * Reset the stringpiece to refer to new data.
     * @param str a pointer to a NUL-terminated string.
     * @stable ICU 4.8
     */
    void set(const char *str);

    /**
     * Removes the first n string units.
     * @param n prefix length, must be non-negative and <=length()
     * @stable ICU 4.2
     */
    void remove_prefix(int32_t n) {
        if (n >= 0) {
            if (n > length_) {
                n = length_;
            }
            ptr_ += n;
            length_ -= n;
        }
    }

    /**
     * Removes the last n string units.
     * @param n suffix length, must be non-negative and <=length()
     * @stable ICU 4.2
     */
    void remove_suffix(int32_t n) {
        if (n >= 0) {
            if (n <= length_) {
                length_ -= n;
            } else {
                length_ = 0;
            }
        }
    }

    /**
     * Maximum integer, used as a default value for substring methods.
     * @stable ICU 4.2
     */
    static const int32_t npos; // = 0x7fffffff;

    /**
     * Returns a substring of this StringPiece.
     * @param pos start position; must be non-negative and <= length().
     * @param len length of the substring;
     *            must be non-negative and will be pinned to at most length() - pos.
     * @return the substring StringPiece
     * @stable ICU 4.2
     */
    StringPiece substr(int32_t pos, int32_t len = npos) const {
        return StringPiece(*this, pos, len);
    }
};

/**
 * Global operator == for StringPiece
 * @param x The first StringPiece to compare.
 * @param y The second StringPiece to compare.
 * @return TRUE if the string data is equal
 * @stable ICU 4.8
 */
U_EXPORT UBool U_EXPORT2
operator==(const StringPiece &x, const StringPiece &y);

/**
 * Global operator != for StringPiece
 * @param x The first StringPiece to compare.
 * @param y The second StringPiece to compare.
 * @return TRUE if the string data is not equal
 * @stable ICU 4.8
 */
inline UBool operator!=(const StringPiece &x, const StringPiece &y) {
    return !(x == y);
}

U_NAMESPACE_END

#endif  // __STRINGPIECE_H__
